A conventional boat drive of the type in which a propeller shaft in a housing connected to the bottom of the hull of a ship or forming an outboard motor or part of a Z-drive can have a transmission in the housing which connects a drive shaft reaching upwardly in the housing to an engine, to a propeller shaft on which the hub of the variable pitch propeller is mounted. The blades are pivotal on this hub by an appropriate mechanism and the propeller shaft may be hollow to accommodate a pusher to adjust the pitch.
In the boat drive of this type described in U.S. Pat. No. 2,850,106, the positioning device for the push rod is located in the hull of the ship and is connected by a transmission with the push rod. The push rod extends only partly through the hollow propeller shaft and carries at an end thereof radial stems which traverse openings in the hollow propeller shaft to reach into the hub. This construction has not found widespread practical utility and has not only structural and functional disadvantages but makes mounting or dismounting of the parts for repair or maintenance time consuming and expensive.
More recent constructions, e.g. as described in European Patent Document EP 0231503, have a more compact construction in which the blade-adjustment stems extend parallel to the propeller shaft. It has been found that, although this system is highly effective, it is capable of improvement with respect to the ability to maintain and repair the unit, can be simplified with respect to the actuation of the pusher rod and, in general, can be improved upon.